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91
Antarctica / Re: Sea Ice Extent around Antarctica
« Last post by Bill Fothergill on March 29, 2017, 12:05:37 PM »
As the ASIF was down for some time, I originally posted the following comments on the current ASIB thread instead.

Every day since the 5th November 2016, Antarctic sea ice extent has been at record low levels. The NSIDC daily Antarctic sea ice extent value for March 27th came in at 3.304 million sq kms. This was a somewhat jaw-dropping 2.037 million sq kms lower than the equivalent figure from last year.

The cumulative effect of just over 20 weeks at record low levels has obviously been dragging down the rolling 365-day annual average extent figure. In fact, for the last 5 days, this average extent value has been dropping at over 5k sq kms each day.

The latest (as at 27th March) rolling 365-day average extent value has now dropped to 10.966 million sq kms. The previous record low average was 10.969 million sq kms (6th Aug 1979 - 4th Aug 1980).

To give a bit more perspective, decadal averages (calculated from the NSIDC monthly values) come out as...

1980-89 11.82 million sq kms
1990-99 12.03 million sq kms
2000-09 12.18 million sq kms
2010-16 12.46 million sq kms

Several weeks ago, on the relevant ASIF thread, I had been demonstrably cautious when I had suggested that the rolling 365-day figure would drop below 11 million sq kms by the end of March, and could likely surpass the previous record low sometime toward the end of April.

CAVEAT: Prior to the 20th Aug 1987, figures were produced on alternate days. Therefore, during that earlier record low period (1979-1980), the rolling 365-day figure actually comprised just 183 data points. The implicit assumption is, of course, that the "missing" days will, on average, tend to be halfway between the before/after dates. Some will be lower, some will be higher, but this should just about even out over the 182 "missing" days.



As LMV has just pointed out yet again (see also his comment #585, and my #583 and #587) there are good scientific reasons behind this latest twist in the Antarctic sea ice saga.

92
Arctic sea ice / Re: The 2017 melting season
« Last post by romett1 on March 29, 2017, 11:54:57 AM »
Latest GFS anomalies until next Wednesday (Climate Reanalyzer). Added 5-day forecast, which is still red all the way from Kara Sea to Beaufort.
93
Science / Re: Trump Administration Assaults on Science
« Last post by Jim Hunt on March 29, 2017, 11:52:10 AM »
Retired Rear Admiral David Titley expresses his views on the House Science Committee hearing later today:

Should Climate Scientists Boycott Congressional Hearings?

We should no longer be duped into playing along with this strategy.

Despite sending many skilled science communicators to testify at the hearings over the years and even when scoring tactical victories, the strategic effect of participating at these hearings has been to sustain the perception of false equivalence, a perception only exaggerated by the majority’s ability to select a grossly disproportionate number of witnesses far removed from mainstream science (it’s not coincidence that Judith Curry, professor emeritus, Georgia Institute of Technology, and John Christy, professor of atmospheric sciences, University of Alabama at Huntsville, are called upon so often by the Republicans).

A better response would be to simply boycott future hearings of this kind and to call out these hearings for what they are: a tactic to distract the public from a serious policy debate over how to manage both the short- and long-term risks of climate change.
94
If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

Uh, this is trivial maths.

If warming from natural variability in the last 40 years is X degrees, and this is typical of the longer-term record (2,000 -10,000 years), and then climate change adds another X, then all the following are true:

1)  Recent warming (X + X = 2X) is unprecedented
2)  Recent warming is only 50% due to climate change, and 50% due to natural variability.
3)  Recent total warming is more than the Barnes ice sheet has seen before, and is sufficient to destabilise it. 

Fundamentally, the straw does not need to outweigh the camel in order to break its back.
95
Science / Re: 2017 Mauna Loa CO2
« Last post by Pmt111500 on March 29, 2017, 11:38:55 AM »
Weekly CO2 Mauna Loa Observatory | NOAA-ESRL
Period Week Atmospheric CO2
Last Week March 12 - 18, 2017 407.06 ppm
1 Year Ago March 12 - 18, 2016 404.69 ppm
10 Years Ago March 12 - 18, 2005 384.39 ppm

There it still is. 5 -> 7. Now I did check the number from the primary source and it is for the 2007. It does not look good to have the coding error remaining on the site. https://www.co2.earth Hello.
96
Arctic sea ice / Re: Arctic sea ice changes: Natural variation vs human influence
« Last post by AndrewB on March 29, 2017, 01:44:14 AM »
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.
...
jai mitchell, did you check where the Barnes ice cap is located? It's on Baffin Island, just across from Greenland. See the attached image.

According to the paper by Gilbert et al, the Barnes ice cap - a remnant from the last ice age - has stabilized some two thousand years ago - and they have physical evidence that it hasn't melted at all since then (cosmogenic radionuclides), despite the 2,000 or so cycles of Arctic sea ice melting/freezing around the Baffin Island. But now, unprecedented warmth in the northeastern Canada and Greenland region is causing the disappearance of the Barnes ice cap.

If half the warming in the northeastern Canada and Greenland region is - as the Ding et al 2014 paper suggests - due to natural variability, how come this "natural variability" has not once affected the Barnes ice cap in the last 2,000 years?

The problem with Arctic sea ice is that we only have a 40 years satellite record, besides the fact that Arctic sea ice comes and goes every year. So the claim by Ding et al that the recent demise of the Arctic sea ice is in a large part due to "natural climate variability", cannot be contradicted with historical data. But not so with the Barnes ice cap. We have a 10,000+ years record - with proper physical evidence - of its existence, and a 2,000+ years record of its relative stability, during which NO "natural variability" climate component affected it.

I fully agree with you that the disappearance of Arctic sea ice is 110% the result of anthropogenic forcing. I would say the same applies to the recent warming of the northeastern Canada and Greenland region, where the Barnes ice cap is located.

The paper by Gilbert et al about the Barnes ice cap supports the assertion that anthropogenic forcing is responsible for the unprecedented warming in the region, "unprecedented" being the key word here. It directly contradicts the claim in the Ding et al 2014 paper that (quoting from the abstract) "... a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability."
97
Arctic sea ice / Re: The 2017 melting season
« Last post by VeliAlbertKallio on March 29, 2017, 01:17:37 AM »
As per animation, the continued southward drift from the Baffin Bay remains one of the sea ice leaking points from the Arctic joining the Fram Strait, the Barentz Sea and the Kara Sea for rapid and early loss of sea ice. The Baffin Bay sea ice loss contribution may not be continuous, but it impacts the onset of darkening and melting of Greenland once sun gets stronger. It suggests me that the area is rapidly clearing from ice by sea ice transport - which is probably early.

ACNFS Hycom Sea ice drift predicted from today to Apr 2.
The situation reminds a bit to Spring 2014, with the ice drifting away from Laptev sea coasts persistently, and a lot of transport toward the Atlantic.
98
Arctic sea ice / Re: The 2017 melting season
« Last post by Tor Bejnar on March 29, 2017, 01:09:58 AM »
The longer that bit of water remains ice-free, the less likely ice will re-cover it, as
1) the open water is prone to solar gain
2) the end of the (local) freezing season approaches.

I'm sure the surface re-freezing remains a possibility, though.  (It's still cold out there!)
99
Permafrost / Re: Negative Feedback of Positive Snowfall Anomalies
« Last post by bbr2314 on March 29, 2017, 12:32:27 AM »
<snip>

If more of the Earth's surface is reflecting more sunlight back into space (and dissipating heat more readily at nighttime as well), I would think that actually has a *larger* impact than changes in GHGs, which alter the distribution of heat retained by the Earth, not the overall amount of heat it actually takes in. The only things that can alter the latter are A) changes in the sun's output or B) changes in the Earth's reflectance/albedo.

<Snip>
My gut feeling on this is that Albedo has been the climate change driver from 1700-ish on. GHGs are just now catching up in importance.

More show fall means more light reflected back to space and more IR radiated to space.  But there is a thread on albedo warming potential.  In that thread the comment was made that snow early has less effect than snow late does.  That is as it relates to Arctic sea ice loss.
I could see that being possible/likely.

But I would actually go back farther than 1700 in terms of GHGs/albedo impact. Not in weighing one more than the other, but in re-thinking our current knowledge of what caused the changes to the earth's climate.

I do not think it is coincidental that the Little Ice Age followed the largest period of human death in our species' history. This period followed three main events; the Mongol conquest and killing of much of Asia, the Black Death, and the discovery of the Americas with the consequent genocide of ~100 million people in that episode alone.

Combined, I think we can clearly see that depopulation was a major driver (or was likely a major driver) of the Little Ice Age. This was probably not just due to a reduction in GHG emissions; the changes to continental albedo must also have been fairly dramatic, and an ensuing uptick in forested areas (although relatively short term) would have also provided a massive carbon sink. Think of all the fields/etc that went fallow & sprouted trees after the people who had tended them for several centuries died of plague, Mongols, or smallpox. That is probably at least several percentage points of Earth's total land mass!

Traveling back further in time, the "Medieval Warm Period" followed the advances and innovations of both Rome and China, which also coincided with the population peak ~1250. And while we like to think of modern humans as some kind of exceptional race, we are anything but -- and this "exceptionalism" also applies to our preconceived notions re: GHGs and the Industrial Revolution (in that, 99.9999% of people believe that GHGs only became significant following the IR).

This is far from true. In fact, papers show that total atmospheric copper emissions from the Romans and Chinese were hugely impressive, and it would take until approximately 1850-1900 for modern emissions to equal that which was put out between 1,500-2,000 years ago! Techniques for industry were dirtier by orders of magnitude compared to today's processes, so even though they may have used less resources than we do today, their processes for extracting and refining were evidently adequate enough to rival the societies of ~1900 Europe in their total emissive capacities.

Going back even further, I suspect that while Milankovitch cycles may have been the primary climate driver pre-humans, early agriculture & late hunter-gatherer societies were equally transformative, and were the point at which humans overwhelmed the global system. The changes to planetary albedo began with the destruction of megafauna, and culminated with the advent of agriculture, both of which affected decent percentages of the planetary land surface despite very low human populations.

Somewhat of a digression, but I find the subject of pre-IR human-induced climate change extremely interesting, and when you consider the historical evidence/coincidences between the planet's climate and human society, it seems that the latter has led the former, and not vice versa.
100
Arctic sea ice / Re: Arctic sea ice changes: Natural variation vs human influence
« Last post by bbr2314 on March 28, 2017, 11:39:41 PM »
have to agree with kt on this, there is nothing in the barnes paper that contradicts Ding et al.  It just shows unprecedented warmth.

these papers, however DO show that 1. Anthropogenic aerosols are the primary driver of north atlantic SST and that 2. North Atlantic SST is determined by NAO conditions, ergo, NAO variability is primarily driven by Aerosol emissions.

The Ding paper only reinforces this as his teleconnection to tropical pacific variability is ALSO well understood to be primarily driven by anthropogenic aerosols.

see:

Booth et al. (2012)
Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability
http://centaur.reading.ac.uk/30590/1/30590booth_et_al_nature_2012-accepted_draft.pdf

“Individually, volcanoes and aerosols explain 23% and 66% of the temporal multidecadal variability (10 year smoothed) of the detrended NASST (Figure S5). Combining both contributions, 76% (80% after inclusion of mineral dust aerosols) of the simulated variance is explained.”

Miettinen et al. (2011)
North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years
https://www.researchgate.net/publication/227298859_North_Atlantic_sea_surface_temperatures_and_their_relation_to_the_North_Atlantic_Oscillation_during_the_last_230_years

“The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship. North Atlantic sea surface temperatures and their relation to the North Atlantic Oscillation during the last 230 years.”

This is very interesting to me. One thing I have noticed since studying history is the seeming correlation between the World Wars and brutally cold winters in Europe. But perhaps it is not merely correlation, but causation?

If aerosols are the primary drivers of global atmospheric patterns then it would stand to reason that as human industrial manufacturing kicks into its highest gears (i.e., during wartime), the plumes of aerosols would drift north forcing more high-latitude "blocking" and consequently allowing much colder air to enter the continents where people actually live.

We saw this happen both during World Wars I and II, especially at the onset of WWII, when 1939-40 was the most brutal winter across much of Europe since the end of the nineteenth century.

http://www.nature.com/nature/journal/v145/n3671/abs/145376a0.html
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